阅读说明：本技术 Sapo-34分子筛和铜基sapo-34脱硝催化剂及其制备方法和应用、脱硝方法 (SAPO-34 molecular sieve and copper-based SAPO-34 denitration catalyst, preparation method and application thereof, and denitration method ) 是由 李歌 王宝冬 孙琦 王红妍 李晶 刘子林 徐文强 李永龙 马少丹 于 2018-06-12 设计创作，主要内容包括：本发明涉及废弃物综合利用领域,公开了SAPO-34分子筛和铜基SAPO-34脱硝催化剂及其制备方法和应用、脱硝方法。SAPO-34分子筛的制备方法包括：(1)将粉煤灰与第一碱液混合进行第一水热反应,得到含硅碱液和含铝残渣；(2)在含硅碱液中通入含有CO<Sub>2</Sub>的气体,得到硅胶；(3)将含铝残渣与第二碱液混合进行第二水热反应,得到含铝碱液；(4)在含铝碱液中通入CO<Sub>2</Sub>气体和调节pH值,得到氧化铝；(5)将氧化铝加入磷酸溶液中并与硅胶进行混合,然后加入模板剂进行老化和水热晶化。本发明充分利用了粉煤灰中的硅铝资源,低能耗可实现工业化生产,制备的铜基SAPO-34脱硝催化剂能够有效降低烟气中氮氧化物的含量。(The invention relates to the field of comprehensive utilization of wastes, and discloses an SAPO-34 molecular sieve and copper-based SAPO-34 denitration catalyst, and a preparation method, application and denitration method thereof. The preparation method of the SAPO-34 molecular sieve comprises the following steps: (1) mixing the fly ash and a first alkali liquor to carry out a first hydrothermal reaction to obtain a silicon-containing alkali liquor and an aluminum-containing residue; (2) introducing CO into the silicon-containing alkali liquor 2 To obtain silica gel; (3) mixing the aluminum-containing residue with a second alkali liquor to carry out a second hydrothermal reaction to obtain an aluminum-containing alkali liquor; (4) introducing CO into aluminum-containing alkali liquor 2 Gas and pH value adjustment to obtain alumina; (5) adding alumina into phosphoric acid solution, mixing with silica gel, adding template agent, ageing and hydrothermal crystallizing. The invention fully utilizes the silicon-aluminum resource in the fly ash, has low energy consumption and can realize industrial production, and the prepared copper-based SAPO-34 denitration catalyst can effectively reduce the content of nitrogen oxides in flue gasAmount of the compound (A).)

1. A preparation method of SAPO-34 molecular sieve is characterized by comprising the following steps:

(1) mixing the fly ash and a first alkali liquor to carry out a first hydrothermal reaction, and filtering to obtain a silicon-containing alkali liquor and an aluminum-containing residue;

(2) introducing CO into the silicon-containing alkali liquor₂Performing first carbonization on the gas, and performing first drying to obtain silica gel;

(3) mixing the aluminum-containing residue with a second alkali liquor to perform a second hydrothermal reaction, and filtering to obtain an aluminum-containing alkali liquor;

(4) introducing CO into the aluminum-containing alkali liquor₂Performing second carbon decomposition on the gas, adjusting the pH value of the aluminum-containing alkali liquor, performing second drying to obtain aluminum hydroxide crystals, and performing first calcination to obtain aluminum oxide;

(5) and adding the alumina into a phosphoric acid solution, mixing the alumina with the silica gel, adding a template agent for aging and hydrothermal crystallization, and performing third drying and second calcination to obtain the SAPO-34 molecular sieve.

2. The method as claimed in claim 1, wherein in the step (1), the feeding weight ratio of the fly ash to the first alkali liquor is 1: (1.5-3); preferably, the first alkali liquor is sodium hydroxide or potassium hydroxide, and further preferably, the concentration of the first alkali liquor is 5-25 mol/L;

preferably, the conditions of the first hydrothermal reaction include: the temperature is 80-100 ℃ and the time is 4-6 h.

3. The method of claim 1, wherein, in step (2), the CO-containing gas is₂In the gas of (2), CO₂The content of (B) is 40-100 wt%;

preferably, the first carbonation condition includes: the temperature is 40-80 ℃, and the time is 1-2 h;

preferably, the conditions of the first drying include: the temperature is 95-110 ℃, and the time is 8-10 h.

4. The method as claimed in claim 1, wherein in the step (3), the feeding weight ratio of the aluminum-containing residue to the second alkali liquor is 1: (1-3); preferably, the alkali liquor is a mixed liquor of sodium hydroxide and calcium hydroxide, and further preferably, the concentration of the second alkali liquor is 15-20 mol/L;

preferably, the conditions of the second hydrothermal reaction include: the temperature is 240 ℃ and 280 ℃, and the time is 4-6 h;

preferably, Na in the aluminum-containing alkali liquor₂The concentration of O is 100-150g/L, Al₂O₃The concentration of (b) is 100-120 g/L.

5. The method according to claim 1, wherein, in the step (4), the pH value of the aluminum-containing alkali liquor is adjusted to 10-12;

preferably, the second carbonation conditions include: the temperature is 20-50 ℃ and the time is 0.5-2 h;

preferably, the conditions of the second drying include: the temperature is 95-110 ℃, and the time is 8-10 h;

preferably, the conditions of the first calcination include: the heating rate is 5-10 ℃/min, the temperature is 800-.

6. The method according to claim 1, wherein in step (5), the molar ratio of silica, template, alumina, phosphoric acid and water in the silica gel is (1.5-2): (8-12): (7-10): (6-8): (40-80);

preferably, the template is an organic amine template, and further preferably, the template is one or more of triethylamine, tetraethyl amine, tetraethyl ammonium hydroxide and morpholine;

preferably, the aging conditions include: the temperature is 20-40 ℃, and the time is 6-10 h;

preferably, the conditions of the hydrothermal crystallization include: the temperature is 170-230 ℃, and the time is 12-48 h;

preferably, the third drying conditions include: the temperature is 95-110 ℃, and the time is 3-8 h;

preferably, the conditions of the second calcination include: the heating rate is 5-10 ℃/min, the temperature is 550 ℃ and 650 ℃, and the time is 6-8 h.

7. The SAPO-34 molecular sieve prepared by the process of any one of claims 1-6, wherein the molecular sieve comprises 30 to 50 wt.% of Al, based on the total weight of the molecular sieve₂O₃6-14% by weight of SiO₂And 36-64% by weight of P₂O₅；

Preferably, the molecular sieve has a microporous structure with a pore volume of 0.08-0.25cm³/g, specific surface area 570-595m²The pore diameter is 1.70-2 nm.

8. Use of the SAPO-34 molecular sieve of claim 7 in MTO, MTP.

9. A preparation method of a copper-based SAPO-34 denitration catalyst, wherein the SAPO-34 molecular sieve of claim 7 is impregnated with a copper-containing solution for transition metal loading, and the copper-based SAPO-34 denitration catalyst is obtained by ethanol rotary evaporation and calcination;

preferably, the concentration of the copper-containing solution is 0.02-0.1 mol/L;

preferably, the dosage of the copper-containing solution is 100-200mL relative to 1g of the SAPO-34 molecular sieve;

preferably, the conditions of the calcination include: the heating rate is 5-10 ℃/min, the temperature is 550 ℃ and 650 ℃, and the time is 6-8 h.

10. The copper-based SAPO-34 denitration catalyst prepared by the method of claim 9, wherein the denitration catalyst comprises 25 to 45 wt.% of Al, based on the total weight of the denitration catalyst₂O₃5-10% by weight of SiO₂35-70% by weight of P₂O₅And 1 to 15 wt% CuO;

preferably, the denitration catalyst has a microporous structure and a pore volume of 0.05-0.2cm³(g) specific surface area of 450-²The pore diameter is 1-1.8 nm.

11. A denitration method, which comprises contacting industrial waste gas containing nitrogen oxides and mixed gas containing ammonia gas, oxygen and nitrogen with the copper-based SAPO-34 denitration catalyst as claimed in claim 10 at the temperature of 100-350 ℃ to carry out denitration reaction; in the industrial waste gas, the volume concentration of nitrogen oxide calculated by NO is 100-1000ppm, the oxygen content in the mixed gas is 3-5% by volume, and the molar ratio of ammonia to the nitrogen oxide calculated by NO in the industrial waste gas is (1-3): 1; the volume space velocity of the total feeding amount of the industrial waste gas and the ammonia gas atmosphere is 3000-150000h^-1。

Technical Field

The invention relates to the field of comprehensive utilization of industrial solid wastes, in particular to an SAPO-34 molecular sieve, a preparation method and application thereof, a copper-based SAPO-34 denitration catalyst, a preparation method thereof and a denitration method thereof.

Background

Fly ash is fine ash collected from flue gas generated after coal combustion, and is main solid waste discharged from coal-fired power plants. The main oxide composition of the fly ash of the thermal power plant in China is as follows: SiO 2₂、Al₂O₃、FeO、Fe₂O₃、 CaO、TiO₂And the like. Along with the development of the power industry, the discharge amount of fly ash of coal-fired power plants is increased year by year, and the fly ash becomes one of industrial waste residues with larger discharge amount in China. A large amount of fly ash can generate dust without treatment, thereby polluting the atmosphere; if discharged into a water system, the river can be silted, and toxic chemicals in the river can cause harm to human bodies and organisms.

As the chemical components of the fly ash contain various available elements (such as aluminum, silicon and the like), the fly ash is a rich resource with great development value. If the fly ash can be effectively recycledThe useful substances can not only develop circular economy and economical economy, but also reduce the damage of ore mining to the natural ecological environment. The main object of the comprehensive utilization of fly ash is alumina (Al) as the main component₂O₃) And silicon dioxide (SiO)₂) In general, high alumina fly ash (alumina content of 35% or more) is selected as a raw material to study the extraction of alumina. The high-alumina fly ash aluminum extraction only aims at the fly ash with the alumina content of more than 35 percent, and the technical route has no universality. The total amount of silicon and aluminum resources in the fly ash accounts for 60-95%, and if the silicon and aluminum resources in the fly ash can be simultaneously utilized, the defects of long and complex technical routes of the step-by-step aluminum and silicon extraction process can be overcome. Therefore, a technical route which can simultaneously utilize silicon-aluminum resources in the fly ash to prepare products with higher added values and is suitable for all fly ashes is urgently sought.

Nitrogen oxides (NOx) are one of the main atmospheric pollutants, causing great harm to human bodies, environment and ecology, and effective control and reduction of the emission of the nitrogen oxides are required to improve the quality of the atmospheric environment. Most current NOx control technologies employ Selective Catalytic Reduction (SCR) denitration technologies. The key of the denitration technology is a catalyst, and the catalyst for general commercial use is V₂O₅-WO₃/TiO₂The optimum active temperature window is higher (300-400 ℃). In order to meet the requirement of the temperature window, a catalytic bed layer is generally arranged in front of a dust remover, and the arrangement method not only can cause sulfur poisoning and dust blockage of the catalyst, but also needs a larger space behind the furnace; v in the active component has toxicity and is not beneficial to ecological environment and body health; in addition, the temperature of flue gas discharged by equipment such as sintering machines and pelletizing machines in steel plants is less than 200 ℃, and the active temperature window of the medium-high temperature SCR catalyst cannot be met, so that the development of the low-temperature SCR technology has very important significance.

In recent years, low-cost and nontoxic molecular sieve catalysts have been favored by researchers because of their advantages of high activity, wide reaction temperature window, appropriate acidity, good stability, and the like. Having NH₃The structure of SCR active molecular sieves is many, such as ZSM-5, BEA, USY, SAPO-34, SSZ-13, etc.

In recent years, fly ash is used as a raw material, and simultaneously, silicon-aluminum resources are efficiently utilized to prepare a silicon-aluminum molecular sieve, which mainly comprises the following steps: a type, X type, Y type, P type, SAPO-34, ZSM-5, beta type and other microporous molecular sieves.

CN103449467A discloses a method for preparing 13X molecular sieve from high alumina fly ash, which comprises: mixing the high-alumina fly ash with alkali liquor to carry out pre-desiliconization reaction, and filtering to obtain desiliconized solution; mixing the desiliconized solution with white carbon black to obtain modified desiliconized solution; mixing the modified desiliconized solution with an aluminum source to obtain a silicon-aluminum sol; and crystallizing, filtering, washing and drying the silicon-aluminum sol to obtain the 13X molecular sieve. The method synthesizes the 13X molecular sieve aiming at the filtrate obtained after the aluminum is extracted from the high-alumina fly ash under the condition of adding an aluminum source, and does not realize the synchronous utilization of silicon-aluminum resources in the fly ash.

CN104291349A discloses a method for preparing a P-type molecular sieve by taking fly ash as a raw material, which comprises the following steps: firstly, pretreating and activating the fly ash; secondly, preparing sodium silicate and sodium metaaluminate by using the activated fly ash; thirdly, synthesizing a P-type molecular sieve: firstly, uniformly mixing a sodium silicate solution and a sodium salt, then dropwise adding the sodium metaaluminate solution into the mixed solution, and finally adding an organic steric hindrance agent and a proper amount of deionized water to form a reaction mixture, wherein the organic steric hindrance agent M is at least one of ethanolamine, diethanolamine and triethanolamine; putting the mixed materials into a polytetrafluoroethylene container, and stirring for 30min at the speed of 100r/min-300 r/min; then putting the mixture into a stainless steel reaction kettle, and carrying out hydrothermal synthesis for 2-8 h at the temperature of 30-140 ℃; and taking out a product in the reaction kettle, centrifugally separating, washing for 3-4 times by using deionized water, and drying for 12 hours at 120 ℃ to obtain the P-type molecular sieve.

CN103787354A discloses a method for preparing MCM-41 molecular sieve by using fly ash, which comprises the following steps: a. drying the fly ash raw powder to constant weight, mixing the fly ash raw powder with HCl solution, stirring, centrifuging, washing and drying for later use; b. mixing and calcining the fly ash treated in the step a and NaOH, cooling and grinding into fine powder, adding the obtained ground calcined substance into deionized water, mixing, stirring, and performing centrifugal separation to obtain a supernatant; c. weighing template CTAB, dissolving in deionized water, continuously stirring under the water bath condition, dropwise adding the supernatant obtained in the step b, adjusting the pH of the solution by using HNO3, continuously stirring to obtain a gelatinous substance, carrying out crystallization reaction on the obtained gelatinous substance, naturally cooling to room temperature after crystallization, centrifuging, washing, drying and roasting to obtain the MCM-41 molecular sieve. The pure silicon molecular sieve obtained by the method does not contain aluminum element and does not realize the synchronous utilization of silicon-aluminum resources.

CN106082267A discloses a method for preparing SAPO-34 molecular sieve from fly ash by microwave hydrothermal coupling, which comprises the following steps: 1) grinding and roasting the fly ash, washing with water, pickling with acid, washing with water, and drying to obtain fly ash microspheres; 2) measuring the content of alumina and silicon oxide in the fly ash microspheres, mixing the fly ash microspheres, phosphoric acid, a template agent and water in sequence according to the content to form a crystallization stock solution, calculating according to the content of alumina in the fly ash, calculating according to phosphorus pentoxide by using phosphoric acid, wherein the mass ratio range is as follows: phosphorus pentoxide: 1: 1-3: 1 of aluminum oxide, and a template agent: 2: 1-6: 1 of alumina, water: stirring the alumina (90: 1-180: 1) to uniformly mix the crystallization stock solution, wherein the ratio is the mass ratio of the substances; 3) transferring the uniformly stirred crystallization stock solution into a hydrothermal kettle with tetrafluoroethylene as a lining, and performing microwave hydrothermal coupling crystallization; 4) and cooling the crystallized solution, taking out, washing, centrifuging, filtering, washing and drying the crystallized product, and then roasting to remove the template agent to obtain the SAPO-34 molecular sieve. The method needs to grind and roast the fly ash at high temperature, thus having large energy consumption and non-green process; and the microwave step is adopted, so that the industrial production is difficult to realize.

As can be seen from the existing documents and patent reports, the research related to the preparation of SAPO-34 molecular sieve by using fly ash is less, and CN106082267A discloses a method for preparing SAPO-34 molecular sieve, but calcination is needed, the energy consumption is higher, and the industrial production is difficult to realize. The denitration catalyst prepared by the prior art does not have good catalytic activity in a medium-low temperature range (300 ℃), and has the defects of short service life, poor high-temperature selectivity, biotoxicity of vanadium and the like.

Disclosure of Invention

The invention aims to solve the problems that in the prior art, the fly ash needs to be calcined, a large amount of energy consumption is needed, industrial production is difficult to realize, and a denitration catalyst has poor catalytic activity and poor selectivity in a medium-low temperature range and has biotoxicity, and provides an SAPO-34 molecular sieve and a copper-based SAPO-34 denitration catalyst, and a preparation method, application and a denitration method thereof. The SAPO-34 molecular sieve and copper-based SAPO-34 denitration catalyst prepared by the method not only fully utilizes the silicon-aluminum resource in the fly ash, but also has the advantages of low energy consumption and realization of industrial production. The SAPO-34 molecular sieve prepared by the invention can be used in MTO and MTP processes. The prepared copper-based SAPO-34 denitration catalyst can effectively reduce the content of nitrogen oxides in flue gas in a medium-low temperature range, and has the characteristics of high activity, high selectivity and no biotoxicity.

In order to achieve the above object, the present invention provides, in a first aspect, a method for preparing a SAPO-34 molecular sieve, wherein the method comprises the steps of:

(1) mixing the fly ash and a first alkali liquor to carry out a first hydrothermal reaction, and filtering to obtain a silicon-containing alkali liquor and an aluminum-containing residue;

(2) introducing CO into the silicon-containing alkali liquor₂Performing first carbonization on the gas, and performing first drying to obtain silica gel;

(3) mixing the aluminum-containing residue with a second alkali liquor to perform a second hydrothermal reaction, and filtering to obtain an aluminum-containing alkali liquor;

(4) introducing CO into the aluminum-containing alkali liquor₂Performing second carbon decomposition on the gas, adjusting the pH value of the aluminum-containing alkali liquor, performing second drying to obtain aluminum hydroxide crystals, and performing first calcination to obtain aluminum oxide;

(5) and adding the alumina into a phosphoric acid solution, mixing the alumina with the silica gel, adding a template agent for aging and hydrothermal crystallization, and performing third drying and second calcination to obtain the SAPO-34 molecular sieve.

In a second aspect, the invention provides a SAPO-34 molecular sieve, prepared by the above method, wherein the molecular sieve is based on total weight of the molecular sieveContaining 30-50 wt.% of Al₂O₃6-14% by weight of SiO₂And 36-64% by weight of P₂O₅。

Preferably, the molecular sieve has a microporous structure with a pore volume of 0.08-0.25cm³/g, specific surface area 570-595m²The pore diameter is 1.70-2 nm.

The third aspect of the invention provides the application of the SAPO-34 molecular sieve in MTO and MTP.

The fourth aspect of the invention provides a preparation method of a copper-based SAPO-34 denitration catalyst, wherein the SAPO-34 molecular sieve is impregnated with a copper-containing solution to carry out transition metal loading, and the copper-based SAPO-34 denitration catalyst is obtained through ethanol rotary evaporation and calcination.

The fifth aspect of the present invention provides a copper-based SAPO-34 denitration catalyst prepared by the method described above, wherein the denitration catalyst contains 25 to 45 wt% of Al, based on the total weight of the denitration catalyst₂O₃5-10% by weight of SiO₂35-70% by weight of P₂O₅And 1 to 15 wt% of CuO.

The sixth aspect of the invention provides a denitration method, which comprises the steps of contacting industrial waste gas containing nitrogen oxides and mixed gas containing ammonia gas, oxygen and nitrogen with the copper-based SAPO-34 denitration catalyst at the temperature of 100-350 ℃ to carry out denitration reaction; in the industrial waste gas, the volume concentration of nitrogen oxide calculated by NO is 100-1000ppm, the oxygen content in the mixed gas is 3-5% by volume, and the molar ratio of ammonia to the nitrogen oxide calculated by NO in the industrial waste gas is (1-3): 1; the volume space velocity of the total feeding amount of the industrial waste gas and the ammonia gas atmosphere is 3000-150000h^-1。

According to the invention, the SAPO-34 molecular sieve and the copper-based SAPO-34 denitration catalyst are synthesized by utilizing the fly ash, so that silicon elements and aluminum elements in the fly ash can be completely converted into effective components in the molecular sieve, the purposes of recycling solid wastes and increasing the additional value of the fly ash are achieved, and the preparation method is suitable for industrial production.

Copper-based SAPO-34 denitration catalyst prepared by the invention and existing denitration catalystCompared with the prior art, the method has the advantages of low cost, high acidity, excellent oxidation-reduction performance, high utilization rate of silicon-aluminum resources, high activity, high selectivity, large specific surface area, good thermal stability, high denitration efficiency, safety and no biotoxicity. At the temperature of 150-350 ℃, ammonia is used as a reducing agent to convert nitrogen oxide into nitrogen, the conversion rate of NOx reaches more than 90%, the denitration window is wide, and N is₂The selectivity can reach more than 95 percent, and no by-product N is generated₂And O is generated. The invention can achieve the purpose of treating wastes with wastes and has good economic and social benefits.

Drawings

FIG. 1 is a process flow diagram for the preparation of SAPO-34 molecular sieve in accordance with the invention;

FIG. 2 is a process flow diagram of the present invention for preparing a copper-based SAPO-34 denitration catalyst;

FIG. 3 is an X-ray powder diffraction pattern of a copper-based SAPO-34 denitration catalyst of the present invention;

FIG. 4 is a graph showing N2 adsorption desorption of the copper-based SAPO-34 denitration catalyst of the present invention;

FIG. 5 is a graph of the denitration efficiency of the copper-based SAPO-34 denitration catalyst of the present invention;

FIG. 6 is N of a copper-based SAPO-34 denitration catalyst of the present invention₂And (4) a selectivity graph.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In a first aspect, the present invention provides a method for preparing a SAPO-34 molecular sieve, wherein a process flow diagram for preparing the SAPO-34 molecular sieve of the present invention can be shown in fig. 1, and the method comprises the following steps:

(1) mixing the fly ash and a first alkali liquor to carry out a first hydrothermal reaction, and filtering to obtain a silicon-containing alkali liquor and an aluminum-containing residue;

(2) introducing CO into the silicon-containing alkali liquor₂Performing first carbonization on the gas, and performing first drying to obtain silica gel;

(3) mixing the aluminum-containing residue with a second alkali liquor to perform a second hydrothermal reaction, and filtering to obtain an aluminum-containing alkali liquor;

(4) introducing CO into the aluminum-containing alkali liquor₂Performing second carbon decomposition on the gas, adjusting the pH value of the aluminum-containing alkali liquor, performing second drying to obtain aluminum hydroxide crystals, and performing first calcination to obtain aluminum oxide;

(5) and adding the alumina into a phosphoric acid solution, mixing the alumina with the silica gel, adding a template agent for aging and hydrothermal crystallization, and performing third drying and second calcination to obtain the SAPO-34 molecular sieve.

According to the method of the invention, the fly ash can be solid waste discharged from a coal-fired boiler and contains alumina, silica and optional magnesium oxide, potassium oxide, calcium oxide, titanium dioxide, iron oxide and the like.

According to the method, in the step (1), the feeding weight ratio of the fly ash to the first alkali liquor can be 1: (1.5-3); preferably, the first alkali liquor is sodium hydroxide or potassium hydroxide, and further preferably, the concentration of the first alkali liquor is 5-25 mol/L.

According to the method of the present invention, the conditions of the first hydrothermal reaction may include, but are not limited to: the temperature is 80-100 ℃ and the time is 4-6 h.

According to the process of the present invention, in the step (2), the catalyst contains CO₂In the gas of (2), CO₂Is contained in an amount of 40 to 100% by weight. When CO is present₂When the concentration of (B) is not 100% by weight, the CO is contained₂The gas may be CO₂And N₂The mixture of (4) is not limited thereto.

According to the method of the present invention, the conditions of the first carbon point may include, but are not limited to: the temperature is 40-80 ℃ and the time is 1-2 h.

According to the method of the present invention, the conditions of the first drying may include, but are not limited to: the temperature is 95-110 ℃, and the time is 8-10 h.

According to the method of the invention, in the step (3), the feeding weight ratio of the aluminum-containing residue to the second alkali liquor can be 1: (1-3); preferably, the second alkali liquor is a mixed liquor of sodium hydroxide and calcium hydroxide, and further preferably, the concentration of the second alkali liquor is 15-20mol/L, wherein the weight ratio of sodium hydroxide to calcium hydroxide is (20-80): (2-6).

According to the method of the present invention, the conditions of the second hydrothermal reaction may include, but are not limited to: the temperature is 240 ℃ and 280 ℃, and the time is 4-6 h.

According to the method of the invention, Na is contained in the aluminum-containing alkali liquor₂The concentration of O is 100-150g/L, Al₂O₃The concentration of (b) is 100-120 g/L.

According to the process of the present invention, in step (4), the pH of the aluminum-containing lye may be adjusted to 10 to 12. The aluminium-containing lye within this pH value is more suitable for obtaining aluminium hydroxide crystals.

According to the method of the present invention, the conditions of the second carbonation may include, but are not limited to: the temperature is 20-50 ℃ and the time is 0.5-2 h.

According to the method of the present invention, the conditions of the second drying may include, but are not limited to: the temperature is 95-110 ℃, and the time is 8-10 h.

According to the method of the present invention, the conditions of the first calcination may include, but are not limited to: the heating rate is 5-10 ℃/min, the temperature is 800-.

According to the method of the invention, in the step (5), the feeding ratio of the silicon source, the template agent, the aluminum source, the phosphorus source and the water, namely the molar ratio of the silicon oxide, the template agent, the aluminum oxide, the phosphoric acid and the water in the silica gel is (1.5-2): (8-12): (7-10): (6-8): (40-80). Wherein the water is added during the addition of the phosphoric acid solution, and the water can be deionized water, distilled water and the like.

According to the method of the present invention, the template may be an organic amine template, and further preferably, the template is one or more of triethylamine, tetraethyl amine, tetraethyl ammonium hydroxide and morpholine.

According to the method of the present invention, the aging conditions may include, but are not limited to: the temperature is 20-40 ℃ and the time is 6-10 h.

According to the method of the present invention, the conditions of the hydrothermal crystallization may include, but are not limited to: the temperature is 170-230 ℃, and the time is 12-48 h.

According to the method of the present invention, the conditions of the third drying may include, but are not limited to: the temperature is 95-110 ℃ and the time is 3-8 h.

According to the method of the present invention, the conditions of the second calcination may include, but are not limited to: the heating rate is 5-10 ℃/min, the temperature is 550 ℃ and 650 ℃, and the time is 6-8 h.

According to a specific embodiment of the present invention, the preparation method of the SAPO-34 molecular sieve can comprise the following steps:

(1) mixing the fly ash and a first alkali liquor to carry out a first hydrothermal reaction, cooling and filtering to obtain a silicon-containing alkali liquor and an aluminum-containing residue;

(2) introducing CO into the silicon-containing alkali liquor obtained in the step (1)₂Performing first carbonation on the gas, fully stirring, filtering, washing and drying to obtain silica gel;

(3) mixing the aluminum-containing residue obtained in the step (1) with a second alkali liquor to perform a second hydrothermal reaction, cooling, filtering, and taking a supernatant for later use, wherein the supernatant is the aluminum-containing alkali liquor;

(4) introducing CO into the aluminum-containing alkali liquor obtained in the step (3)₂And (4) carrying out second carbonation and pH value adjustment, drying to obtain aluminum hydroxide crystals, and carrying out first calcination to obtain aluminum oxide.

(5) And (3) adding the alumina obtained in the step (4) into a phosphoric acid solution by adopting a hydrothermal crystallization method, stirring, adding the silica gel obtained in the step (2) into the solution, adding a template agent, fully stirring, aging, placing in a crystallization kettle for hydrothermal crystallization, filtering, washing with deionized water, drying, and calcining to remove the template agent to obtain the SAPO-34 molecular sieve.

In a second aspect, the invention provides a SAPO-34 molecular sieve, prepared by the above method, wherein the molecular sieve contains 30 to 50 wt.% of Al, based on the total weight of the molecular sieve₂O₃6-14% by weight of SiO₂And 36-64% by weight of P₂O₅。

In the invention, the molecular sieve has a micropore structure and a pore volume of 0.08-0.25cm³/g, specific surface area 570-595m²The pore diameter is 1.70-2 nm.

The third aspect of the invention provides the application of the SAPO-34 molecular sieve in MTO and MTP.

The fourth aspect of the invention provides a preparation method of a copper-based SAPO-34 denitration catalyst, wherein the SAPO-34 molecular sieve is impregnated with a copper-containing solution to carry out transition metal loading, and the copper-based SAPO-34 denitration catalyst is obtained through ethanol rotary evaporation and calcination. The process flow diagram for preparing the copper-based SAPO-34 denitration catalyst can be shown in FIG. 2.

According to the method of the invention, the concentration of the copper-containing solution may be 0.02-0.1 mol/L. Preferably, the copper-containing solution is used in an amount of 100-200mL relative to 1g of the SAPO-34 molecular sieve. Further preferably, the conditions of the calcination may include, but are not limited to: the heating rate is 5-10 ℃/min, the temperature is 550 ℃ and 650 ℃, and the time is 6-8 h.

The fifth aspect of the present invention provides a copper-based SAPO-34 denitration catalyst prepared by the method described above, wherein the denitration catalyst contains 25 to 45 wt% of Al, based on the total weight of the denitration catalyst₂O₃5-10% by weight of SiO₂35-70% by weight of P₂O₅And 1 to 15 wt% of CuO.

In the invention, the denitration catalyst has a microporous structure and a pore volume of 0.05-0.2cm³(g) specific surface area of 450-²The pore diameter is 1-1.8 nm.

The sixth aspect of the invention provides a denitration method, which comprises the steps of contacting industrial waste gas containing nitrogen oxides and mixed gas containing ammonia gas, oxygen and nitrogen with the copper-based SAPO-34 denitration catalyst at the temperature of 100-350 ℃ to carry out denitration reaction; in the industrial waste gas, the volume concentration of nitrogen oxide (calculated by NO) is 100-1000ppm, the oxygen content in the mixed gas is 3-5% by volume, and ammonia gasThe molar ratio of the nitrogen oxide to the nitrogen oxide in the industrial waste gas calculated as NO is (1-3): 1; the volume space velocity of the total feeding amount of the industrial waste gas and the ammonia gas atmosphere is 3000-150000h^-1。

The present invention will be described in detail below by way of examples.

In the following examples, the chemical composition of fly ash is shown in Table 1.

TABLE 1